1. Field of the Invention
The present invention relates to a slide fastener with a slider locking mechanism capable of automatically locking a slider without use of any resilient member.
2. Description of the Related Art
As a conventional slide fastener for use in clothes, there has been known a type in which a slider having a locking mechanism is inserted through an element row in order to prevent right and left fastener stringers from being opened unintentionally when the slider is not operated. Generally, the slider having the locking mechanism has a locking pawl capable of advancing to and retracting from an element guide passage formed between upper and lower blades of the slider and a leaf spring for urging the locking pawl into the element guide passage. When the slider is not operated, the locking pawl is urged by the leaf spring so as to engage a part (pawl portion) of the locking pawl with the element row, thereby stopping movement of the slider.
By the way, as a measure to environmental problems in recent years, it has been demanded to form respective components which constitute a product of the same material in order to facilitate recycling of materials. However, in sliders having the above-described conventional locking mechanism, for example, often the slider and tab are molded of synthetic resin while the leaf spring having resilience is formed of a metallic member. That is, in many cases, the leaf spring is formed of a different material from the other members. For the reason, when recycling the materials of the slider, its components need to be separated, thereby taking time and labor, which is a problem of the prior art.
Although a resilient member such as the leaf spring is sometimes formed of synthetic resin in order to solve the problem about recycle, usually, the resilient member made of synthetic resin is likely to be deteriorated with a time passage so that the resilience is lost with a long term usage, which is another problem.
A slider with a locking mechanism configured of components made of the same material without use of any leaf spring considering the recycle of the slider has been disclosed in Japanese Patent Laid-Open Publication No. 2000-333710. Further, U.S. Pat. No. 2,972,793 has disclosed a slider with a locking mechanism without use of any leaf spring.
In the slider described in Japanese Patent Laid-Open Publication No. 2000-333710, all its components are formed of synthetic resin and more specifically, the slider is constituted of four synthetic resin components, a slider body, a tab, a locking pawl (pawl) and a cover body for attaching the tab to the slider body. The tab has a mounting shaft (pintle) for attaching the tab to the slider body rotatably and a cam having a thumb-shaped section provided projectingly at right angle with respect to the longitudinal direction of the tab from the mounting shaft.
In the slider of Japanese Patent Laid-Open Publication No. 2000-333710 having such a structure, when the tab attached to the slider body is held at a non-operation position by rotating the tab to a rear mouth side, the locking pawl accommodated in the slider body is pressed by the cam. Consequently, the locking pawl presses right and left element rows and at the same time, a part of the locking pawl is fitted into between elements, thereby locking the slider.
U.S. Pat. No. 2,972,793 has described a slider 81 with a locking mechanism in which as shown in FIG. 13, a tab 82 includes a mountain-like locking pawl 83 and a hook-shaped retractable pawl 84 (see FIG. 2 of U.S. Pat. No. 2,972,793). According to U.S. Pat. No. 2,972,793, the retractable pawl 84 is a pawl which first engages an element row 85 when the tab 82 is pushed down, and if the fastener is moved, when the tab 82 is at a non-locked position, the retractable pawl 84 and the locking pawl 83 are retracted into a locked position. That is, in the slider 81 of U.S. Pat. No. 2,972,793-A1, when the retractable pawl 84 is retracted into an element row 85, the tab 82 is rotated so that the locking pawl 83 engages the element row 85 to thereby lock the slider 81.
In the slider made of synthetic resin described in Japanese Patent Laid-Open Publication No. 2000-333710, when the locking pawl presses the element row while a part of the locking pawl fits into between the elements, the slider is locked easily. However, to lock the slider in this way, a user needs to rotate the tab and press the locking pawl with a cam provided on the tab. That is, the slider cannot be automatically locked.
Further, according to Japanese Patent Laid-Open Publication No. 2000-333710, because the cam and locking pawl of the tab receive a large load when the slider is locked, the cam and locking pawl are worn as a result of repeated usage in a long period. Consequently, a locking function of the slider is lowered or becomes inoperative. Additionally, while the slider of Japanese Patent Laid-Open Publication No. 2000-333710 is constituted of four members, the reduction in the number of the components of the slider has been demanded in views of reduction of manufacturing cost and ease of assembly.
In the slider 81 described in U.S. Pat. No. 2,972,793, when the fastener is moved as described above, the retractable pawl 84 is retracted into the element row 85 so that the tab 82 is rotated. Thus, the slider can be locked without user's rotating the tab unlike the slider of Japanese Patent Laid-Open Publication No. 2000-333710.
However, because in the slider 81 of U.S. Pat. No. 2,972,793, two small pawls different in shape, the locking pawl 83 and retractable pawl 84, need to be formed for the tab 82, the configuration of the tab 82 becomes complicated and the size of the slider 81 tends to be enlarged. Further, U.S. Pat. No. 2,972,793 has no description about the positions and the dimensions of the locking pawl 83 and the retractable pawl 84 which are formed in the tab 82. In the slider 81 of U.S. Pat. No. 2,972,793, it is important to set up positions and dimensions of the locking pawl 83 and the retractable pawl 84 appropriately. The locking pawl 83 is worn considerably or the slider 81 cannot be locked stably depending on the positions and dimensions of the locking pawl 83 and the retractable 84.